This invention relates generally to molded polymeric containers, and more particularly to methods for making overmolded containers, which may enhance certain functionalities of the container, such as surface texture and hand feeling, coloration and other visual design variables, thermal insulation, and other functions.
Polyethylene terephthalate (PET) based polyesters have been widely used as container materials because of their good mechanical properties and barrier properties. Containers made from PET, however, typically have hard and smooth surfaces. These surfaces are difficult to grip, and containers can slip from a consumer's hand, causing the container contents to spill. This loss of grip is often exacerbated when a filled container product (e.g., a bottle containing a beverage) that has been stored at low temperature (e.g., in a refrigerator) is taken out for use at room temperature such that water condenses onto the outside of the container. It therefore would be highly desirable to improve the grippability of PET containers, as well as other thermoplastic polymeric containers, especially for product containers that frequently find use in conditions under which condensation forms on the outside of the containers. As used herein, the terms “grippable” and “grippability” refer to the characteristic of a surface of a container that one is able to hold firmly, without slipping from one's grasp.
As PET has found increasingly more applications in the beverage and consumer goods industry, brand owners are pressed to identify ways to differentiate their products, particularly through packaging innovation. Examples of innovative design features include the use of different textures on the containers and colored containers. While many of these marketing innovations may be conceptually appealing, their implementation may not be practical from a manufacturing, cost or environmental perspective, or the container may possess certain characteristics that would render the design unsuitable in other aspects. For example, colored containers can severely damage the PET recycling stream because they cannot be easily separated from the remaining PET stream. Furthermore, a textured mold is required to make a textured container. Such molds often are very expensive, and it is difficult to change the texture once the mold is created. It therefore would be desirable in the industry to be able to differentiate a PET packaged product without a detrimental impact on the PET recycling stream or an excessive cost increase.
Overmolding or multi-component molding has been widely used in the injection molding industry. Overmolding is essentially defined as a process that produces finished components with two or more thermoplastic based resins by way of injection molding. Overmolding has been used in the cable industry for many years, and has found increasing interest in the industrial and consumer goods industries. In these industries, many applications combine a soft touch material with rigid parts. The soft touch materials provide improved aesthetics, better tactile properties, and improved grippability. The most widely used method of combining a soft and rigid material is by overmolding. Traditionally, overmolding of the soft material directly onto the rigid material creates the finished product part. It would be desirable to provide a way to use soft touch materials with rigid containers, such as beverage containers.
A need therefore exists in the packaging industry to create a container that is easily colored, with controllable gripping functions, insulation functions, and/or other functions, and to achieve these design features without negatively impacting the PET or other thermoplastic recycling stream. Furthermore, there exists a need in the packaging industry to create such a container with a cost-effective process.